package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.sql.Wrapper;
import java.util.Arrays;
import java.util.List;

/**
 * @author HuanyuZhou
 * @date 2020/4/23 14:36
 */
public class DefaultSqlSession implements sqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {

        //将要完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectone(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if(objects.size() == 1){
            return (T) objects.get(0);
        }else{
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }

    }

    @Override
    public Integer updateOne(String statementId, Object... params) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.update(configuration,mappedStatement,params);
    }


    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层都还是去执行JDBC代码 //根据不同情况，来调用selectList或则selectOne
                //准备参数 1：statementid ： sql语句的唯一标志：namespace.id = 接口全限定名.方法名
                //方法名
                String methodName = method.getName();
                //接口权限定名
                String className = method.getDeclaringClass().getName();
                String statementId = className+"."+ methodName;

                //准备参数2: params:args
                //获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();

                if(genericReturnType.getTypeName().equals("java.lang.Integer")){
                    Integer integer = updateOne(statementId, args);
                    return integer;
                }
                //判断是否进行了 泛型类型参数化
                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);

                    return objects;
                }




                return selectone(statementId,args);
            }
        });
        return(T) proxyInstance;
    }


}
